Aruruu is Eruruu's sister. She is shy around strangers but quickly befriends them if they offer honeycomb and then eat it once she offers some back to them. In a sense, she is the druid of the forest, or perhaps 'beastmaster' might be more appropriate. She adopts the cub (naming her Mukuru) of the legendary Mutikapa, an iron-furred tiger who the villagers (under Hakuoro's guidance) killed for their own survival. After Mukuru grows up (to be massive), Aruruu rides her to battle to help her "Father" (she slowly accepted Hakuoro has her surrogate father). Once Hakuoro and his surrogate family move to the castle, Aruruu becomes friends with Kamyu and the blind, sick Yuzuha. Much later, she names a very rare (and very expensive) beast "Gacatar", which acts as the small furry animal mascot. Gacatar also happens to be useful in combat, being able to call down lightning and capable of shrieking at an ultra-sonic, skull-cracking pitch.
Aruruu likes to be petted and stroked like a puppy and hates the goopy feeling of medicine that Eruruu rubs on her after she gets stung while getting honeycombs. She gets along well with her sister, meaning she causes lots of headaches for her. The anime does not show her cunning side - twice she has led angry, unwanted adults into natural traps.